Linux Inetrview questions

 1).what is suid and guid into linux os ?


suid command :


chmod u+S filename


guid command:


chnod g+s filename


2).what types of files are typically in the /etc directory into linux os ?


here we can see the configurations files


3).explain the entries of /etc/fstab file ?


cat /etc/fstab command :



we have a six entries are there:


1).partitions


2).mount points


3).defaults


4).xfs -filesystem


5).0 = dump = which is used to backup of the filesystem


6).0 = fsck = which is sued to checking the filesystem errors and repairing the filesystem


4).what is stickybit,how it will be useful expalin with example?



5).How to provide access to single file to multiple useres and groups with custommized permissions?


using acl you can provide the access to directory/file for mulriple useres and groups


setfacl -m u:tom:rwx /etc/fstab command



6).what is suid and sgid explain ?


7).How to scan for new LUN without server reboot?


we cn install the yum install sg3_utils


we can wexcute the command like as the,


sg_scan -i command


echo "---" > ls /sys/class/scsi_host/hosts

it will lit out the host details . like as the,


host 0,host 1 ,host 2


then we can scan the all hosts one by one.


so we can execut ethe comamnd like as the,


echo "---" > ls /sys/class/scsi_host/host1/scan


8).what is zombie process?. How zombie process will impact system performances?


using top and ps command also we can check it out the


zombie process



Zombie processes in Linux are sometimes also referred to as defunct or dead processes. They're processes that have completed their execution, but their entries are not removed from the process table.


its kind of child process.

9).How to craete single filesystem size more than 3TB in size?


10).what is umask and how umask will be calculated?


11).explain crontab fildes with exaplmes


12).mount point usage is 99% .however did not find any files to delete ,how did you clear up the usage and bring back to normal usage?



first we have to check deleted temp files:


so we can execute the command like as the,


lsof | grep deleted


next we need to clear tmp files by killing pid's:


lsof | grep deleted | grep ."TMP" | awk '{print ,$2} ' | process name kill -9



we need to delete temp files


lsof | grep deleted | grep ".tmp"| awk '{print $9} ' | process name rm -f




https://www.youtube.com/watch?v=0_CPP7OKt6o


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